Mesoscopic Damage and Fracture Characteristics of Hard Rock under High-Frequency Ultrasonic Vibration Excitation

Ultrasonic high-frequency vibrational fracture technology can compensate for the deficiencies of traditional fracture methods and has promising applications in underground rock drilling engineering. In this study, ultrasonic high-frequency vibrational tests were performed on brittle fine-grained red sandstone in combination with CT real-time scanning, which revealed mesoscopic fracture processes in the rock. Digital image processing technology is used to identify and extract the pores of CT images, and the pore evolution law of rock slices at different layers under ultrasonic vibration excitation is quantitatively studied. The results show that the increase in porosity decreases with increasing distance from the excitation surface, with the lowest layers of the rock showing an increase in porosity of only 0.22%. In addition, a mechanical model of rock breaking by ultrasonic vibrations was derived to explain the non-uniform damage mechanism of rock space under ultrasonic vibration excitation.